It is known that the use of electric current to stimulate nerves and other anatomic structures can have positive therapeutic benefits. The alteration of nerve activity through the delivery of electrical stimulation has been defined as neuromodulation or neurostimulation, which will be used interchangeably herein along with electrostimulation. One significant use is for control of pain. Prior to such uses, for many decades, only medications were available. Neuromodulation devices began with implantable systems and moved to transcutaneous ones.
Historically, neuromodulation devices have most effectively accomplished therapeutic results by invasive measures. More specifically, the patient has an electrode or coil surgically implanted directly onto the nerve being targeted for stimulation and also has a signal generator surgically implanted under the skin. The signal generator is connected to the stimulation electrode and passes current to the electrode. Medtronic, for example, developed a line of Deep Brain Stimulation (DBS) implants under the names Soletra® and Kinetra®, but they are no longer sold. Some of these implants that are currently being sold use the trade name Activa® and mitigate symptoms of movement disorders, such as Parkinson's Disease. These devices are implanted typically in patients who are not able to use drugs for treatment.
Another system includes both implanted and external devices. In such a configuration, the patient has an electrode or coil surgically implanted directly onto the nerve being targeted for stimulation, and a signal generator separate from the electrode or coil is used to stimulate transcutaneously the coil site by placing an active electrode on the skin in proximity to the implant. The powered signal generator passes electromagnetic radiation or magnetic flux to, thereby, excite the passive coil and induce it to emit its own electromagnetic emission. These systems employ induction measures for nerve stimulation, referred to as IMNS.
One type of neuromodulation using these implanted devices is vagus nerve stimulation, a procedure that stimulates the vagus nerve with electrical impulses. The vagus nerve (Cranial Nerve X) originates from the brainstem as two separate nerves, which travel down the neck and chest and coalesce into one nerve with multiple branches that innervate organs in the thorax and abdomen. Vagus nerve stimulation can be used to treat epilepsy when other treatments have not worked adequately, for example. Vagus nerve stimulation has also been used as a treatment for depression, and is being studied to treat other conditions such as multiple sclerosis, migraine, weight loss, motion disorders, insomnia, management of pain, obesity, and Alzheimer's disease, to name a few. Historically, with vagus nerve stimulation, a stimulation device is surgically implanted at or about the vagus nerve and a signal generator is surgically implanted under the skin, for example, near the clavicle in the chest. A wire is threaded under the skin connecting the signal generator to the stimulation device at the vagus nerve. When activated, the signal generator sends electrical signals along the vagus nerve, which can either travel to the brainstem and have therapeutic effects on the brain, travel down the vagus to affect various end-organs that are supplied by this nerve, block physiologic nerves signals traveling along the vagus, or send signals simultaneously to the brain and to one or more end-organs normally supplied by the vagus or to the brain only.
Electrostimulation can be used on any nerve or organ to have various therapeutic benefits. Directing modulated current to any cranial nerve could be used to affect the brain due to their natural anatomic connection to the brainstem. For example, electrostimulation of the trigeminal nerve or its branches may be able to block the perception of pain of the head and face or mitigate these symptoms by causing endorphin release from the electrical signal that travels up to the brain.
Cyberonics, Inc., sells a set of vagus nerve stimulators, each being an implantable device. They are sold under the trade names AspireHC™, Pulse™, and Demipulse™. Cyberonics received FDA approval for treatment of epilepsy with their implants in 1997. Any implantable device carries the risks associated with anesthesia such as stroke and death, as well as the risk of damage to vital structures surrounding the vagus and vocal cord paralysis, and the risk of infection at the surgical site. If the device were to break or need to be adjusted, another surgery would be required. Additionally, batteries that power the implanted generators for these devices eventually wear down and must be replaced, requiring surgery with associated risks for each generator change.
Another implanted device uses induction as a means to send a signal to an implanted device that is surgically placed on the vagus nerve. A removable collar is considered the device charger and is worn around the patient's neck. Therapy is planned and programmed from a portable electronic tablet. With such a device, the risks of surgery, as listed above, still exist, in addition to the unsightly and cumbersome nature of a dog-collar style necklace.
Less invasive devices that exist use transcutaneous needle arrays. One example of such a system is disclosed in U.S. Patent Publication No. 2013/0150923 to Schnetz et al., and is sold by Biegler GmbH under the trade name P-STIM®. A significant drawback of such systems is that the needle electrodes break the skin, causing pain and the consequent patient aversion, as well as an increasing risk of infection.
Non-invasive devices that are as or more effective would be desirable, for example, one that is utilized transcutaneously. Some devices employ Vagus Nerve Stimulation (VNS) transcutaneously in an attempt to reproduce the effects of implantable devices. For example, electroCore developed a transcutaneous VNS device that looks like a stun-gun and is placed on the neck over the vagus nerve. When activated, the device provides electric stimulation to the neck when a patient feels the onset of a seizure. electroCore's device is sold under the name gammaCore®. Due to the depth of the vagus nerve at that treatment location, such devices place a large electrical signal directly to the carotid artery when in use. Patients experience significant intolerance to such high levels of electrical energy, as well as incur the possibility of closing the artery, or dislodging plaque or a clot, if sufficient pressure is applied over the treatment period. Additionally, it is known that electrical energy supplied to blood vessels can cause vasoconstriction. Thus, there is the dangerous possibility that the physical pressure exerted on the carotid could be enhanced by the electrical energy and shut the artery during treatment. In addition, significantly more current is needed to traverse more interposed tissue, which is accompanied with an increase in discomfort and can adversely affect other structures.
In contrast to the electroCore device, Cerbomed GmbH developed a transcutaneous VNS device under the name NEMOS®. The cell-phone-like controller connects to a non-adjustable earpiece that places two electrodes on the skin of the concha of the ear at two specific points. The earpiece serves as scaffolding that retains the position of the electrodes and maintains constant contact forces of the electrodes against the skin of the target area within the concha of the ear. The earpiece is retained with an “earbud-like” component that resides in the ear canal inferiorly and under the “conchal ridge” superiorly. Retention is dependent upon constant vertical spring forces that have to be substantially strong enough to avoid movement of the apparatus. The force required to accomplish this is poorly tolerated over the prolonged required treatment periods because of the very thin skin of the outer ear canal that the device is contacting, as well as the high degree of sensitivity of the ear in this location. Such apparatuses in or about the ear canal can impair hearing and negate the ability to use earphones for simultaneously listening of music. Additionally, the superior retention point of the apparatus has a very thin skin, has minimal subcutaneous “padding,” and is very non-compliant. Further, the surface area of contact of the retention device is limited in comparison to the force required to retain the device, making the retention forces very concentrated and painful. The limited surface area contact causes high resistance, poor signal transmission, and increased pain. If the spring force was reduced to gain comfort, the earpiece would no longer be retained well and the electrode contact against the skin would become suboptimal or lost completely. Further, the superior and inferior anchoring points only lend to placing the electrodes at a specific location on the ear. This location may not be ideal for the therapeutic benefit that such devices are intended to have. Therefore, the Cerbomed earpiece design does not lend itself to electrode placement at any other anatomic locations about the ear. This apparatus is not resistant to motion from routine human activity, such as walking quickly, running, collision with others and other objects, such as tree branches, crowds, wind, etc. Furthermore, the cord interfacing with the earpiece is disposed of inferiorly and applies a downward force not only due to its own weight but also when it gets caught or snagged on other objects. The vertically grounded retention elements of the earpiece submit to these forces and easily dislodge and subsequently disrupt proper contact or dislodge the necessary electrode interfacing with the skin.
Transcutaneous VNS uses the fact that the auricular branch of the vagus nerve (ABVN) supplies the skin of the concha in the human ear. The NEMOS® generator applies electrical signals that are known in the art to these two points. To overcome the resistance of the skin, this device provides a very high level of energy that patients find difficult to tolerate.
Another neuromodulation device for treatment of migraines takes the form of a headband and is sold by Cefaly-Technology, Inc. It is known that most headaches and migraines involve the trigeminal nerve. Its superior branch (supra-orbital) ends at the exit of the eye socket, underneath the skin of the forehead. The Cefaly® headband connects to an adhesive electrode on the forehead. Through the electrode, the headband generates modulated electrical signals to stimulate the nerve endings of the trigeminal nerve. Neuromodulation of the trigeminal nerve with Cefaly® helps reduce the frequency of migraine attacks. Efficacy of this device relies on maintaining proper contact to the skin during the entire treatment duration and this is why the Cefaly® headband has significant negative characteristics. The adequacy of maintaining electrical contact is very inconsistent and can vary based on the storage temperature of the electrode, the ambient temperature during application and use, the stability over time of the adhesive, relative humidity, skin thickness, skin oil levels, thickness of the underlying tissue, and potential allergies to the substances within the adhesive. Also, the surface area of the electrode is large, and resides on the forehead, making it unsightly, hot, and visually disruptive in certain locations such as the workplace. Electrode removal can be painful as it strips underlying hair from the forehead. It is also cumbersome to apply a large adhesive bandage to one's own forehead and then be required to interface it with a generator as a multistep process. Finally, the device causes painful muscle contractions during use.
Current transcutaneous devices have not achieved good results for a multitude of reasons. First, current transmitted through the skin in order to target an anatomic structure inside the body results in poor signal strength to the target structure, poor localization of the target structure, and difficulty with signal transmission through the barrier of the skin and surrounding structures. Further, the high current has collateral physiological effects to the surrounding non-targeted structures. In addition, the degree of user coupler apposition to the skin is not maintained as a constant by present devices. This leads to variation in impedance, which can adversely affect the degree of transmission of the electromagnetic signal through the skin and, therefore, change the effectiveness of the signal in reaching the target structure. Moreover, maintenance of position at the location where the user coupler is in contact to the external portion of the body has been a challenge due to variability of adhesives that adhere to skin and due to discomfort of any devices that use strong springs or other mechanical measures to maintain position. Additionally, fixation of the user couplers that are secured secondarily to a structure remote from the targeted skin interface location frequently lose their indexing due to body motion and environmental contact. Loss of position on the skin by the user coupler leads to the signal not being maintained on the targeted internal structure, which adversely leads to ineffectiveness of the device. Furthermore, optimal locations at which stimulator user couplers are recommended to be placed on the body surface are constantly changing due to ongoing and evolving scientific research, thus making obsolete user couplers that are designed only for a specific anatomic location. For systems that do not include a coupler, the user then becomes the coupling mechanism for the device, requiring steady hands to hold the device in a precise location to deliver the electrical signal to the desired underlying nerve structure throughout the duration of the therapy.
User couplers of prior art neuromodulation devices and systems are not scalable to differing anatomies, require anatomies to be similar and/or consistent, are not universal, do not maintain consistent and adequate contact during daily activities, are unsightly, and are uncomfortable, and, when used about the ear, the prior art devices obstruct the auditory canal, are dependent upon obstructing the ear canal, and preclude other auditory canal systems. With regard to the generator elements of the prior art, they are not modulated or subject to external input, they are not synchronized with audio signals, and there are no features to improve patient tolerance.
As can be seen, there is a need for systems and methods that provide an external, transcutaneous stimulator that maintains constant signal transmission to the desired target, maintains electrodes at constant pressure and constant location for maximum efficacy, maintains position of the user coupler on the body's interface location, and can be modified easily to place electrodes at alternate interface locations without the need for changing device hardware.
It is well known that effectiveness of central nervous system (CNS) stimulation by sending electrical signals through the cranial, peripheral, or central nerves that are remote from the brain has been demonstrated to treat various conditions such as epilepsy, depression, obesity, systemic inflammatory disorders, depression, sleep disorders, tinnitus, poor concentration, attention deficit disorders, heart disease, arrhythmias, pain, and chronic pain, to name a few. Studies have shown that effectiveness, as well as effectiveness for any given disease or disorder, relates to the type of electrical signal generated (i.e., wave type/wave geometry, pulse width, dwell time, using pulse bursts, pulse duration, power, and patterns of administration of therapy such as varying the amplitude of the current with or without variations of some or all of the aforementioned parameters). A certain minimal power threshold must be met to have a therapeutic benefit. As an upper power threshold has not been established, it is well accepted that there exists a “therapeutic range” of power that, on the low end, is the minimal power requirement to have any documentable therapeutic benefit. Increasing the power of the electronic signal above that therapeutic threshold appears to have a greater benefit. The problem facing advancing neuromodulation devices and methods is whether or not an individual patient can tolerate the discomfort associated with the delivery of a signal delivered at the power necessary to maximize therapeutic benefit.
Due to the inconvenience of the application process of current transcutaneous neuromodulation devices and the inability to deliver therapy in a discrete way, users may choose to delay therapy until they have privacy and a dedicated amount of time for the treatment. This additionally limits access to non-pharmacologic therapies that can treat a multitude of chronic diseases, symptoms, and conditions.
It would be beneficial to provide systems and methods for allowing a patient to tolerate uncomfortable electronic signals delivered. Thus, a need exists to overcome the problems with the prior art systems, designs, and processes as discussed above.